Handle a Microsoft Edge v0.11 bug with Array.from:

http://www.ecma-international.org/ecma-262/6.0/#sec-array.from says that "if mapFn is undefined, let mapping be false", which means it doesn't matter if it's provided undefined, or not provided. Edge v0.11 only ignores it if it's not provided.

es6-shim.js

@@ -1018,6 +1018,21 @@
   if (!arrayFromSwallowsNegativeLengths || !arrayFromHandlesIterables) {
     overrideNative(Array, 'from', ArrayShims.from);
   }
+  var arrayFromHandlesUndefinedMapFunction = (function () {
+    // Microsoft Edge v0.11 throws if the mapFn argument is *provided* but undefined,
+    // but the spec doesn't care if it's provided or not - undefined doesn't throw.
+    return valueOrFalseIfThrows(function () { return Array.from([0], undefined); });
+  }());
+  if (!arrayFromHandlesUndefinedMapFunction) {
+    var origArrayFrom = Array.from;
+    overrideNative(Array, 'from', function from(items) {
+      if (arguments.length > 0 && typeof arguments[1] !== 'undefined') {
+        return _apply(origArrayFrom, this, arguments);
+      } else {
+        return _call(origArrayFrom, this, items);
+      }
+    });
+  }
 
   var toLengthsCorrectly = function (method, reversed) {
     var obj = { length: -1 };